In chapter 5 of Play Optimal Poker 2, Andrew Brokos explains how stack-to-pot ratio (SPR) reshapes hand values, leverage, and optimal strategies, especially on the flop. He shows that once the flop is dealt, thinking only in big blinds is misleading—you must think in terms of how big the pot is relative to remaining stacks.
SPR, Pot Odds, and What “Strong” Means
Brokos starts by tying SPR directly to equity requirements:
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At SPR 1, if someone shoves pot for the full stack, you risk 1 pot to win 2 more (3 total), needing about 33% equity.
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As SPR increases, you must:
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Risk a larger amount relative to the pot,
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Expect your opponent’s stack-off range to be stronger,
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And therefore need both more equity and a stronger hand class to continue profitably.
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This leads to two big ideas:
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Stack-off thresholds rise with SPR.
Top pair may be plenty at SPR 2, marginal at SPR 5, and trash at SPR 50. -
Draws age better than many made hands as ranges tighten.
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Bottom set is a monster at moderate SPRs but can be in awful shape against only higher sets at SPR 100.
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Nut draws rarely dominate the field, but their equity remains resilient as villain’s range gets stronger, especially if they draw to the best possible hand.
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So, at high SPR, nut draws are often better candidates to pile money in than middling made hands that are easy to dominate.
Shallow-Stacked K♦ 8♦ 8♣: SPR 15 vs SPR 4 vs SPR 1
We revisit the now-familiar scenario:
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$1/$2, Ivan (UTG) raises to $6.
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Opal defends her big blind.
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Flop: K♦ 8♦ 8♣, effective stacks vary.
The chapter compares how optimal flop play changes when they start the flop with very different SPRs.
Who Benefits from Lower SPR?
At SPR 15 (deep), Ivan’s positional and range advantage lets him torture Opal’s condensed range across multiple streets with leverage. At SPR 4:
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Opal’s EV actually rises slightly.
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Out of position, she now has fewer future decisions, which reduces how much she can be outplayed.
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The smaller remaining stack limits Ivan’s leverage—he simply can’t threaten as many pot-sized bets later, so Opal’s bluff-catchers are under less future pressure.
At very low SPR (around 1), the game tilts even more toward “who has equity right now,” and away from positional brilliance.
Ivan’s Strategy at Low SPR
At SPR ~4
With $52 behind and $13 in the pot on the flop:
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The solver solution creates a small checking range (~8%) for Ivan.
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In theory he does slightly better by checking some hands like QQ, JJ, TT, AQ, AJ, and occasionally KK.
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These hands:
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Don’t love facing a check-raise,
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Still win often in small pots,
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And benefit from protection via a stronger checking range.
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But the gain is tiny. In practice, Brokos says you can simply keep betting your entire range for a small size and not worry about the slight improvement.
However, continuation bets are less profitable than at SPR 15:
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Check-raises now threaten a much larger fraction of Ivan’s stack.
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When he bets weak hands, Opal can shove profitably more often.
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Leverage has shrunk, so his “auto-profit” c-bets disappear.
At SPR ~1
With something like $13 effective on the flop:
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Ivan now checks about half his range.
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Strong hands don’t need to build the pot—any single bet can get stacks in.
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Weak hands no longer gain as much from bluffing, since there’s little room to fold Opal off better hands on later streets.
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Medium-strength hands (like AJ, 77, naked overcards with future potential) benefit from checking:
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They retain their equity,
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Avoid getting blown off draws or backdoors by a check-shove,
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And live inside a checking range that contains enough monsters to protect them.
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In short: the shallower the stacks, the more Ivan must protect his equity by checking.
Opal’s Strategy at Low SPR
More Check-Raises, Less Calling
At SPR 4:
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Opal’s check-raise frequency jumps from ~12% (deep) to over 20%–28%, depending on whether Ivan has a checking range.
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Why? Because:
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Hands like KQ and KJ are now strong enough to play for stacks.
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The cost of being wrong is smaller.
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Ivan will stack off lighter given the low SPR.
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She now:
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Check-raises more Kx for value,
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Uses that expanded value range to support more bluff check-raises.
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At the same time:
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Her folding frequency also rises (from ~29% to high 30s at SPR 4, and about 40% at SPR 1).
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She starts folding small pairs without a diamond that she would have stubbornly defended deep.
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These hands no longer have enough implied odds to justify calls.
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Meanwhile, the check-raises with strong Kx are so profitable that giving up some thin calls is a good trade.
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At SPR 1:
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Opal mostly plays raise-or-fold versus a flop bet.
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Her calling range shrinks to a small core of hands (strong trips, some mid pairs, a few strong draws).
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A practical simplification: just shove or fold against the c-bet and rarely flat-call.
Preflop Planning: Choose Hands for the SPR You Expect
Brokos stresses that you shouldn’t treat preflop and postflop as separate games. You must pick hands based on the SPR you expect on the flop:
When SPR Will Be High (5+)
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Favor big suited and/or connected hands:
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Suited connectors, suited aces, high suited broadways.
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Their value comes from:
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Making straights and flushes that can win very big pots.
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Having strong draws you can use as aggressive tools when deep.
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Small pairs and offsuit aces are less attractive, especially out of position, because:
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You won’t make sets/strong hands often enough,
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And it’s hard to build big pots when you do from OOP.
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When SPR Will Be Low (≤ 4–5)
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Favor big-card hands that flop top pair / top pair–good kicker:
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ATo, AJo, KQo become much more appealing.
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Drawing hands lose value because:
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You won’t be paid enough when they hit.
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There’s less scope to semi-bluff using leverage.
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In 3-bet and 4-bet pots, making the SPR small is precisely why you raise with AA, KK, AK—you want one pair to be enough to stack off.
Practical “Test Yourself” Insights
The chapter includes several applied cases; a few core patterns:
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With deep stacks, you should:
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Prefer hands like A4s and 98s over ATo and 22 from early position, since suited/connected hands take better advantage of high SPR.
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With short stacks (e.g., 15bb):
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Hands like ATo jump in value.
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Hands like A4s, 22, 98s lose a lot because straights, flushes, and sets don’t get paid enough.
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When defending from the big blind with shallow stacks, you can:
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Call a bit wider vs raises because position matters less and your equity realization improves.
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But postflop, you tend to check-raise more aggressively when you connect, especially with top pair or strong draws.
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Key Lessons from Chapter 5 (Rephrased)
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Think in SPR, not big blinds, after the flop.
The risk (stack) only makes sense relative to the reward (pot). -
Low SPR lowers the bar for getting all-in.
Hands that would be “just OK” deep can be effective “nuts” when only one pot-sized bet fits in. -
Position shrinks in value as stacks shrink.
With shallow stacks, there are fewer decisions and less room to outplay people postflop. -
As stacks shorten, tighten late-position opens and continuation-bet less often.
Your bluffs have less leverage and face more profitable check-raises. -
At low SPR, out-of-position players should check-raise more.
Top pairs and strong pairs become stack-off hands; those extra value raises justify more bluff raises too. -
At high SPR, draws often outperform marginal made hands for big-pot planning.
Nut draws in particular keep good equity even as villain’s range gets stronger.